1. Field of the Invention
The present invention generally relates to nuclear medicine, and systems for obtaining nuclear medicine images of a patient's body organs of interest in conjunction with other detection systems. In particular, the present invention relates to a system and method for the tomographic and limited angle tomographic emission acquisition while remaining outside the field of view of accompanying scanning devices for multiple modality imaging.
2. Description of the Background Art
In the field of medicine there has been development of various imaging and scanning devices to aid in the treatment and diagnoses of patients. Many of these devices require considerable amounts of space, and furthermore, if testing requires use of different imaging devices, substantial amounts of time in addition to space is required to conduct the separate scans. In many cases such as in operating rooms or RT rooms, space is at a premium. Moreover, many of the devices have different clinical strengths, where some are effective at indicating functional aspects of the target, such as blood flow in the brain, others are effective at indicating structural aspects, such as bone structure or organ anatomy. Therefore, different imaging devices have been combined to improve the efficiency of hospitals and other medical facilities in the effective use of time and space, and also to enable multiple modality imaging to combine the different strengths of various imaging devices and offset their weaknesses as standalone systems.
Examples of scanning devices which can be used as standalone systems or integrated for dual modality scanning are Single Photon Emitted Computerized tomography (SPECT) and Computed Axial Tomography (CT), as well as positron emission tomography (PET), as well as Magnetic Resonance Imaging (MRI), as well as treatment systems such as Intensity-Modulated Radiation Therapy (IMRT). Such systems can be combined with each other in any number of dual modality combinations for example CT/SPECT, CT/MRI, PET/MRI, and CT/IMRT. Examples of such combined systems are shown in U.S. Pat. Nos. 7,075,087, 6,631,284, and 6,490,476, each incorporated by reference herein in its entirety.
One of the difficulties in integrating such systems for multiple modalities is their inherent space and operating requirements. CT/MRI/PET systems require a particular field of view (FOV) free of impediments that may block the view of the detectors used by the system. Therefore the operation of one system cannot be such that it interferes with the FOV of another system, thereby preventing it from carrying out its scanning activity.
Currently, in many of the ectography and tomography techniques, the patient is scanned by directing the detection devices on some orbit either fully or partially fulfilling the well-known Orlov conditions for tomography. Often, with such systems, the patient bed is used to move the patient, while the detection systems, with a gantry, follow some specified path about the patient in order to fulfill conditions to allow for an appropriate dataset. Such operational requirements prevent simultaneous scanning and unencumbered access to the patient, thereby preventing appropriate care of the patient and effective use of technology and medical facility resources.
Furthermore, current art concerning triple modality systems only envisage aligning the modalities along the tomographic axis (the longitudinal axis of the patient), which make such devices too large. However, certain aspects of SPECT imaging systems have been developed which may lend themselves to use of triple modalities and concurrent full patient access.
In particular, the SPECT system is a nuclear imaging technique wherein radiopharmaceuticals are introduced into the body, either by injection or ingestion, and are attracted to specific organs, bones or tissues of interest. Such radiopharmaceuticals produce gamma photon emissions that emanate from the body and one or more detectors are used to detect the emitted gamma photons. Collimators are placed in front of the detectors to permit only those beams of radiation emanating along a particular path to pass through to be detected by the detector, so that no scattered or environmental background photons are detected. The information is then processed and used to create tomographic images of the patient. Many different schemes and methods of detection have been employed, from using differently shaped collimators to different placement and rotations of the detectors to achieve a full sampling of the target patient.
What is needed therefore, is a method or device which provides for the integration of SPECT with other modalities without impeding the FOV of the separate accompanying scanning devices and providing full access to the patient.